Ed Yong: Suicidal wasps, zombie roaches and other parasite tales

Ed talks through tales of Parasites taking control of other creatures, showing sometimes when humans interpret an animal’s actions they may not always be in complete control of them. Ed is fascinated by parasites, because they eschew simple stories – the reasons behind something involving a parasite are not always obvious.

Artemia and Tapeworm – when Artemia (tiny Bring shrimp) are infected by tapeworm, they change in many ways. When hijacked they are castrated, live longer, become bright red, and swim in packs. This makes them more visible, and more tempting targets for flamingos. Artemia are simply a vehicle to get a tapeworm inside a flamingo, and by swimming in packs they are not being sociable or safety in numbers, they are exposing themselves more for the benefit of their parasite.

Suicidal Cricket infected by horsehair worm. The worm grows to adulthood inside a cricket, but needs to get to water to mate. It addles the cricket’s brain to drive it to behave erratically and eventually drown in water.

A caterpillar is attacked by a parasitic wasp, and continues guarding the larvae of the wasps inside its cocoon.

A cockroach infected by a wasp has venom injected directly to the brain. This overrides the cockroach’s wanting to escape, and it instead follows the wasp to the lair where it gets injected with embryos. Eventually the embryos kill their host and burst from it.

Toxoplasma Gondii (Toxo) can infect many mammals, but can only reproduce in a cat. If it gets into a rodent, the rat will run towards a cat (against normal rat instincts), get eaten, and allow toxo to reproduce.

Humans also attempt manipulation of others, but their attempts are crude compared to the perfect chemicals of the insects. However, the widespread use of parasites in nature makes you wonder if we are ourselves being manipulated. Toxo for example infects 1 in 3 humans, and while they show no overt symptoms these people can score slightly different results in personality tests. Toxo infected humans also show increased rates of schizophrenia.

While humans are different, there’s no reason to think that we are the only animal NOT to be influenced by parasites.

Although this talk was given some three years ago the question that it raises for me is could “toxo” be a contributor to those who may be diagnosed with dementia ? Have there been any studies into this possibility? I am no science major but after digesting your talk the subject seemed plausible.